The present invention relates to an integrated circuit device which incorporates a read only memory (ROM) storing an applications program.
With recent developments in IC techniques, an integrated circuit device incorporating a data processing unit (CPU) and a ROM which stores an applications program has been developed. In such a device, instructions can be internally applied from the ROM to the CPU which constitutes a main part of the device. Therefore, the number of input/output terminals can be reduced to provide compact and inexpensive devices. In such an integrated circuit device, function diagnosis of the CPU and the ROM can be performed by executing instruction of one or more steps stored in the ROM and by thereafter comparing the results with expected values. In this case, a test program for an initial condition setting and a test complete condition decision is provided from the ROM. In such a test system, the test program is arranged in the address space of the ROM. Therefore, the applications program must be prepared in consideration of the test program. In other words, in the address space occupied by the test program the applications program or data cannot be arranged. Accordingly, the address space for the applications program is reduced. For example, when 4-K words of a 64-K word address space are assigned to the test program, the applications program must be arranged within the remaining 60-K word address space.